Best antivirus software: tried and tested

We've tested and reviewed both free and paid-for antivirus software. We bombarded each one with tens of thousands of threats to see how well it can cope against viruses, ransomware and phishing attacks, which are designed to compromise and steal data. 

We repeat this three times a year, as new threats are emerging all the time and want to be sure the best antivirus we recommend will consistently protect your computer.

You can save up to £129 a year by choosing a good free antivirus, which stays active unless shut down or replaced. But be careful, because while the best free antivirus in our tests has as strong (and in some cases, stronger) protection from malicious software than paid-for alternatives, the worst are plagued with irritating pop-ups and aren't as good as rivals at protecting your computer.

Paid-for antivirus comes with a host of useful features, so it could be worth investing in. Typically, you'll find a low price for the first year of protection and a higher renewal price for year two onwards. The renewal price varies by manufacturer but usually costs noticeably more.

The best free antivirus from our tests

Only logged-in Which? members can view the free antivirus test results below. 

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The free antivirus we tested

All the free antivirus we tested are listed in alphabetical order below.

Only logged-in Which? members can view the free antivirus test results. 

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Avast One Basic

Available from avast.com

Most recently tested December 2024

Additional features Firewall, safe banking mode, PC tune-up tool, ad blocking (Chrome browser)

Need to know Free, one licence

AVG Antivirus Free

Available from avg.com

Most recently tested December 2024

Additional features Safe banking mode, ad tracker blocking feature (Chrome browser only), do not disturb mode

Need to know Free, one licence

Do you use a Mac? See our expert pick of the best antivirus for Macs

Avira Free Security

Available from avira.com

Most recently tested December 2024

Additional features Basic VPN, basic tune-up tool, password manager (extension for Chrome and Edge browsers only) 

Need to know Free, one licence

Bitdefender Antivirus Free For Windows

Available from bitdefender.com

Most recently tested December 2024

Additional features None

Need to know Free, three licences

The best paid antivirus from our tests

Only logged-in Which? members can view the paid antivirus test results below. 

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The paid antivirus we tested

All the paid antivirus we tested are listed in alphabetical order below.

Only logged-in Which? members can view the paid antivirus test results. 

Join Which? to get instant access to our test results and Best Buy recommendations.

Avast One Silver

Available from avast.com

Most recently tested December 2024

Additional features Firewall, VPN, tune-up tool

Need to know Paid, initial price £33, renewal price £65, three licences 

AVG Internet Security

Available from avg.com

Most recently tested December 2024

Additional features Firewall, limited banking protection (Fake Website Shield), game mode (do not disturb)

Need to know Paid, initial price £42, renewal price £65, one licence 

Avira Internet Security

Available from avira.com

Most recently tested December 2024

Additional features Basic VPN, tune-up tool, password manager (extender for Chrome and Edge browsers only) 

Need to know Paid, initial price £48, renewal price £48, three licences

Bitdefender Internet Security

Available from bitdefender.co.uk

Most recently tested December 2024

Additional features Basic VPN (separate download), parental controls, SafePay banking protections, password manager (add-on for Chrome and Firefox browsers) 

Need to know Paid, initial price £55, renewal price £55, three licences

ESET Home Security Essential

Available from eset.com

Most recently tested December 2024

Additional features Parental controls (separate download), banking protections 

Need to know Paid, initial price £45, renewal price £90, three licences 

F-Secure Internet Security

Available from f-secure.com

Most recently tested December 2024

Additional features Parental controls, banking protection

Need to know Paid, initial price £60, renewal price £110, one licence 

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G Data Internet Security

Available from gdatasoftware.co.uk

Most recently tested December 2024

Additional features Parental controls, banking protection (G Data BankGuard), secure backup (encrypts backups on Dropbox and Google Drive)

Need to know Paid, initial price £44 (US $56), renewal price £93 (US $120), three licences 

McAfee Total Protection

Available from mcafee.com

Most recently tested December 2024

Additional features VPN, password manager, app boost feature

Need to know Paid, initial price £25, renewal price £80, one licence 

Norton 360 Standard

Available from norton.com

Most recently tested December 2024

Additional features VPN, password manager add-on, comprehensive tune up tool, 2GB cloud backup

Need to know Paid, initial price £28, renewal price £65, three licences 

Sophos Home Premium

Available from sophos.com

Most recently tested December 2024

Additional features Parental controls, banking protection

Need to know Paid, initial price £50, renewal price £90, 10 licences 

TotalAV Internet Security

Available from totalav.com

Most recently tested December 2024

Additional features VPN, tune-up tool, ad blocker, game mode (do not disturb)

Need to know Paid, initial price £129, renewal price £129, six licences 

Trend Micro Internet Security

Available from trendmicro.com

Most recently tested December 2024

Additional features Parental controls (off by default), banking protection (Pay Guard add-on for all browsers), tune-up tool (called PC Health Checkup), game mode (mute notifications)

Need to know Paid, initial price £60, renewal price £60, three licences 

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How we test antivirus

Protection from malware

We fire three batches of malware at antivirus over a year of testing to ensure standards haven’t slipped and the antivirus remains effective against the latest malware. Our specialist lab operates ‘honeypots’, which are like digital fishing nets designed to capture thousands of strains of murky malware and viruses. We have more than 60 honeypots around the world and these capture up to 400,000 files every day and up to 146m over a year.

We use 10,000 samples of unique malware to test each antivirus. We ensure that the antivirus software doesn't let you pass on infected files to other people, even if the files haven’t been opened by you first. Antivirus that pesters you with confusing messages and warnings or wrongly zaps a file that you actually want to use (known as a false positive) are punished in our testing.

Ability to avoid scams

Most antivirus products claim to protect you from scam webpages and emails. To test this, we click on links contained in phishing emails – hoax emails sent in the hope that the recipient will enter confidential information, or click on a dodgy link or open a dodgy attachment. 

This is so we can measure whether the antivirus stops you from proceeding to these dangerous scam websites designed to steal your data or infect your machine. We throw in a few genuine emails, too, to see whether the software wastes your time by flagging emails and websites that are safe for you to access.

Easy to install and use

We buy and install each antivirus on a ‘fresh’ computer and rate this process, including what is and isn’t included. For paid-for software, we also rate how easy it is to stop the software licence from automatically renewing (and charging you) after it expires.

When installed, we rate the initial setup process and first scan, looking to see if it's beginner friendly. We look for security software that not only identifies threats, but warns you clearly and talks to you in jargon-free language. Points are deducted for confusing or scaremongering alerts (especially if the motive is upselling) and any ambiguous action that could compromise security.

Extra features

The main things that separate paid-for and free antivirus are the added extras they come with. If you’re spending money on protection, then you should expect an array of additional and potentially useful features. If the supposedly premium features aren’t worth the money, we’ll flag that to you. 

It may be that a free antivirus – which are increasingly comparable with paid-for antivirus – will meet your needs just as well. It's also worth noting that some features may be exclusive to Windows versions of antivirus. 

Will it slow down my computer?

Virus protection scans should operate silently and discreetly in the background, without reducing your system to a crawl while they carry out their routine virus checks. 

We undertake a range of everyday tasks on our test computer while the software operates and compare this with the performance when the antivirus wasn't installed. We flag any antivirus that makes simple tasks – such as opening a web browser or saving files – take ages. This is known as our 'use of resources' assessment. 

We regularly revisit the antivirus on sale to see if there are any more popular brands that need testing and when we find them, we do.

Why you can trust us: at Which? we're free from manufacturer and retailer influence. Find out more about our impartiality and how your support helps us to stay editorially independent.

Do Windows devices need antivirus?

Windows Defender comes preinstalled with Windows 10 and 11 and for the most part it provides decent security coverage. Plus, Defender is free, it updates with the operating system, quietly works in the background and even includes a few features, such as parental controls and a basic tune-up. 

It has several basic protections that are suitable for everyday browsing, but its limitations lie in areas such as scanning. Based on our tests, it can take multiple scans before it detects (and then acts on) malware, including from connected devices such as USB sticks.

We also didn't find its anti-ransomware capabilities (Defender Security) particularly strong. Its anti-phishing, handled by Microsoft Smart Screen technology, identified some of the well-known phishing test pages we threw at it, but it missed newer examples entirely. Here, the difference between Defender and even the worst antivirus on test is stark.

While Windows' built-in security is OK, if you're looking for more in-depth and dedicated online security, antivirus will be a necessary upgrade. This doesn't have to cost a penny, as you can shore up Defender's weaknesses by selecting a first-class free antivirus.

Free antivirus vs paid-for antivirus

The quality of free antivirus and its ability to detect threats is becoming comparable to many of the best paid-for equivalents. Over the last few years of testing, free antivirus consistently now ranks among the best scoring software on test, and this year is no different.

Increasingly, the main difference between the free and paid-for antivirus from the same company is the additional features offered. Our testing has highlighted that the core protection against malware and phishing is largely identical – this was the result for both Avira and Bitdefender's free and paid-for antivirus. 

One factor that's still a problem for a lot of free antivirus is advertisements and upselling. However, some of the best free antivirus on test only has subtle ads and upselling that can be easily ignored.

If you can go without additional features and endure some ads, it's likely that a top-notch free antivirus is the best choice for you and your bank balance. We've even seen some extra features included with free antivirus, such as basic VPNs and password managers.

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Key features for antivirus protection

• Anti-phishing Whether antivirus protects you from scam websites. Sometimes you're required to install a browser extension for this.
• Backups Some antivirus includes additional safe storage to back up files, folders and pictures, storing them on the antivirus's cloud. This also helps secure important docs from ransomware attacks as the backups are stored within the antivirus companies secure databases and/or cloud service. If you don't renew your antivirus subscription, you'll lose access and the data may be deleted entirely after your subscription ends. Be sure to check the T&Cs for confirmation. Find out more about the best cloud storage.
• Parental controls Used to control access to the internet and programs. These can limit access at specific times of the day or block certain sites entirely.
• Password manager Whether you get access to (either within the main antivirus or via a web browser extension) a password manager tool.
• Tune-up Whether it's capable of scanning and clearing your device of junk or duplicated files, folders and pictures, which manufacturers claim will help to prevent the device from slowing down. Some also monitor applications and deactivate those not in use.

Ransomware: what it is and how to stop it

Ransomware is a type of virus that locks up your system or encrypts the files on your PC, holding you to ransom and demanding payment for you to regain access. Even if you do pay, this doesn't necessarily mean that cybercriminals will restore your access and, even if they do, they may still be able to monitor activity on your PC.  

Cybercriminals are sneaky with their ransomware scams, sometimes even pretending to be the police. They may accuse you of downloading illegal material or adult content to trick or embarrass you into paying a fee.

There are some simple steps to avoid falling victim to ransomware:

• Be careful about any unsolicited messages or emails you receive. Don't download attachments you've not been expecting or click on links that are trying to persuade you to give away personal details. You can always contact a company directly if you want to check if a message is genuine.
• Only download software and apps from a trusted source, such as the Microsoft Store, and reputable software manufacturer's online stores.
• Always keep your PC operating system and any downloaded apps or other software updated. This allows you to benefit from the latest security protections.
• Windows 10 and 11 allow you to turn on a setting that protects folders from unauthorised programs such as ransomware. To turn it on, open the Windows Security app (select the shield icon from your Taskbar – if you can't see it, click Show hidden icons, which looks like ^). Scroll down, select Ransomware protection and click Controlled folder access to turn it on.
• Set up a restore point in case your device is compromised and you need to restore your device from safe mode. To do this, type 'create a restore point' into your PC's search panel. Click Create a restore point and a pop-up box will appear, then click Create. Name your restore point (for example, the month and year) and click Create. Once finished, your PC will confirm and you can click Close.

A quality antivirus – whether paid-for or free – can also provide superb anti-ransomware protection. The best antivirus on test can prevent wide-scale hijacking of your files and device overall. 

Some antivirus also offer features which provide further protection. An example of this would be Norton's 2GB cloud backup where you can protect files. 

How to remove ransomware

If you see a message demanding a fee to regain access to your files or parts of your computer, don’t panic, and certainly don't pay the fee – there's no guarantee they will honour the deal and release your files. Plus, you'll be revealing your bank details to the attackers.

Disconnect your computer from the internet, as the malware might be trying to send out your data to the attackers. To do this in Windows, right-click the wi-fi symbol on your Windows taskbar (at the bottom of your screen). Select Open Network & Internet Settings. In the left-hand column, click Wi-Fi and, in the next window, select the Wi-Fi toggle to switch it off. If it's directly plugged in to your router via an Ethernet cable, just unplug it.

If your PC is locked (meaning that when you boot it up you're immediately confronted by the ransomware message), you’ll need to put it in safe mode. To do this, complete the following steps:

• From the sign-in screen, press and hold your keyboard's Shift button, while you click on Power and then Restart 
• After your PC has restarted, you should now see a blue screen titled 'Choose an option'. Click Troubleshoot, click Advanced options, click Startup Settings and Restart.
• After your PC restarts again, you should see a list of options. Select option 4 and this will enable safe mode.

As long as you've regularly set system restore points on your PC, then from the Safe Mode boot screen you can revert to a state before your PC was infected.

Should you use Kaspersky antivirus?

In 2017, the National Cyber Security Council (NCSC), an arm of intelligence agency GCHQ, recommended government departments do not use Kaspersky due to Russia‘s history of attempting to hack critical UK infrastructure. 

The NCSC published further advice in March 2022. The key thing for UK consumers using Kaspersky software to know is unless they're doing work that could be seen as being counter to the interest of the Russian state, the NCSC says it’s highly unlikely they will be targeted directly. 

However, the NCSC did warn that: ‘You may need to move to a new AV [antivirus] product if Kaspersky itself becomes subject to sanctions, since the AV product would likely stop getting updates (and AV software is only effective if it's updated regularly).' 

As of April 2025, this advice remains unchanged, but we're monitoring what action the British government may take after the US announcement of a ban of Kaspersky software there. We will update this information should a ban of Kaspersky software in the UK be announced. You can find out more on the NCSC website. 

For now, we recommend people stick to alternative antivirus to eliminate the risk of potential upheaval and unprotected devices should Kaspersky be banned or withdraw from the UK market. There are also a variety of alternative antivirus available, including superb free options.